Platinum group metals (platinum, palladium, rhodium, iridium, ruthenium and osmium) are commonly used in catalytic applications. The catalytic reactions take place at the surface of the metal, so it is usual to maximise the surface area of the metal by dispersing small particles of the metal on the surface of a support material. The support material is often an oxide material, and may be a functional oxide material that alters the catalytic activity of the metal by a metal-support interaction (MSI). The metal may be deposited onto the support material by techniques wherein a metal salt is contacted with the support material so that a catalyst precursor is adsorbed onto the support. The support material is heated to a high temperature to decompose the precursor to the catalytically active form of the metal.
For many applications the catalyst is deposited onto a flow-through substrate such as a monolith, foam, static mixer or heat exchanger unit. It is possible to deposit a support material onto the substrate and then subsequently deposit a platinum group metal onto the support material. Alternatively, the platinum group metal may be deposited onto the support material and then the catalysed support material may be deposited onto the substrate.